1. Field of the Invention
The present invention relates to an image processing apparatus, and specifically, relates to a technique of executing quantization processing by an error diffusion method and a dither method using a common circuit.
2. Description of the Related Art
Image data having a large number of gradation levels expressed by multiple values is converted into image data having a smaller number of gradation levels by quantization and thereby print data is generated in a printing apparatus such as an inkjet printing apparatus. Conventionally, in this quantization, processing by a dither method (hereinafter called “dither processing”) and processing by an error diffusion method (hereinafter called “error diffusion processing”) are executed using a common circuit (Japanese Patent Laid-Open No. H06-233122 (1994)). Thereby, it becomes possible to perform quantization effectively utilizing the respective advantages of the dither method and the error diffusion method.
In Japanese Patent Laid-Open No. H06-233122 (1994), however, the dither method and the error diffusion method share only common functions; a comparator circuit comparing a pixel value expressed by image data with a threshold value and a circuit generating the threshold value. Specifically, except for the comparator circuit and the threshold value generation circuit, the dither processing and the error diffusion processing use respective individual circuits. Therefore, there is a problem such as one that it is not possible to effectively reduce a circuit scale by the configuration for sharing described in Japanese Patent Laid-Open No. H06-233122 (1994).